1. Field of the Invention
The present invention relates generally to weapon firing control devices and methods, and, more particularly, to a weapon firing inhibitor for use with a tank-mounted weapon on a test firing or training range.
2. Related Art
Conventional weapon fire control or inhibitor systems often used electrical or electromechanical technology to provide the desired fire control or inhibition. Representative of these systems is U.S. Pat. No. 2,391,473 to Mullen which shows a system which inhibits a gun mounted on an aircraft from firing while a portion of the aircraft is in the line of fire of the gun. A photocell is separated from a light source by an opaque screen so that movement of the gun causes the screen to move relative to the light source and the photocell. The screen has openings which are arranged to cause the photocell to be illuminated by the light source whenever the position of the gun brings the aircraft into its line of fire. Specifically, the incident light upon the photocell energizes a solenoid coil which renders the gun inoperative.
A similar system is shown in U.S. Pat. No. 2,450,551 to Harrington, Jr. The Harrington, Jr. system is for a weapon mounted on a ship. A photocell is illuminated by a light source through an opening in an opaque screen whenever the weapon is aimed away from the ship. The absence of light upon this photocell renders the weapon inoperative. Thus, the weapon cannot inadvertently fire on the ship.
The Mullen and Harrington, Jr. systems are limited to protecting only the structures of the supporting vehicle. In contrast, on a firing range and in actual combat environments, it is desirable that the weapon be inhibited from firing unless it is aimed properly at a target: this is needed in order to protect objects on the range, populated areas beyond the normal projectile impact zone, "friendly" equipment on the battlefield, and the supporting vehicle itself.
One approach used to achieve these goals has been to inhibit the firing of a weapon whenever it receives an electromagnetic signal from the object at which it is aimed. For example, U.S. Pat. No. 3,400,393 to Ash shows a weapon safety mechanism which utlizes an electromagnetic wave receiving means to inhibit a small arms weapon from firing when aimed at a person (1) wearing a transponder radiating the proper electromagnetic wave or (2) wearing a garment or other device capable of reflecting the electromagnetic wave radiated by transmitting means associated with the weapon. Another approach is that shown in U.S. Pat. No. 2,472,136 to Whitlock. In Whitlock, a transponder located on each protected object or vehicle radiates a coded electromagnetic wave upon detecting a pulse-modulated electromagnetic wave radiated by the weapon having a fire control mechanism. In turn, the weapon receives the coded electromagnetic waves and is inhibited from firing at those objects from which it has received such signals.
Conventional systems using this approach give protection only to those objects from which the weapon receives an electromagnetic beam or signal. However, any other object on the battlefield or on the test range without the transmitting equipment providing the electromagnetic beam or signal that is properly detected is in danger of being fired upon. A more effective approach is to identify that which constitutes a proper target(s) or object(s) as opposed to identifying all "improper" targets or objects: this approach allows such improper targets or objects to be present even if they are unforeseen.
In accordance with this approach, conventional systems used on test firing ranges equip intended targets or objects with electromagnetic transmitters which enable the weapon tested only when it is aimed in a manner so that it receives an electromagnetic beam from an intended target. Representative of such conventional systems are those shown in U.S. Pat. No. 2,042,174 to Foisy, U.S. Pat. No. 3,945,133 to Mohon et al and U.S. Pat. No. 4,349,337 to Pardes. Each shows a simulation training device which indicates that a weapon has "hit" an intended target on a screen when an electromagnetic detector on the weapon is aligned with an electromagnetic beam reflected off the target screen. Note that each of these systems utilizes weapons which receive an electromagnetic beam in lieu of firing an actual bullet or projectile.
This approach also has been applied to situations in which live ammunition is fired at targets on a test range. Representative of such conventional systems is that of U.S. Pat. No. 3,703,845 to Griew, which teaches a small arms test firing range in which a hand-held weapon is enabled whenever a receiver on the weapon receives a continuous infrared beam from a transmitter located near an intended target. Reception at the weapon of the infrared beam from the target indicates that the weapon is properly pointed towards the target.
However, the Griew system exhibits several deficiencies or limitations, particularly with respect to large caliber vehicle-mounted weapons test firing over extended firing distances at intended targets. Specifically, the Griew system uses a continuous wave infrared source at the target which needs to be accurately detectable only over the range of a hand-held weapon (which is practically limited to less than a few hundred meters). In contrast, the range of a large caliber weapon (typically several hundred to several thousand meters) increases the distance by an order of magnitude over which such infrared source must be accurately detectable. In such a case, large amounts of power would be required to transmit a continuous wave infrared beam of a sufficient intensity so as to overcome the attenuation produced by the atmosphere and the interference caused by ambient radiation (such as sunlight and heat propagated by heated objects). The signal-to-noise ratio that can be obtained for a given power level over the extended distances present in test ranges for large caliber weapons is significantly reduced due to, among other things, radiation of substantially the same frequency emitted by the sun, and the dispersion of the transmitted beam due to dust, rain and other environmental conditions. The reduced signal-to-noise ratio deteriorates the detectability of the transmitted continuous wave signal. Note that a transmitter capable of generating a continuous wave signal of such power would be large (and thus of limited portability) and costly to manufacture and maintain. In addition, an infrared signal is not seen by the human eye, which would prevent a visual confirmation of the signal by a weapon operator.
Another deficiency or limitation of the Griew system is that the detector circuit of the weapon being test fired is susceptible to improper or "false" triggering by flashes of radiation such as that produced by the reflection of sunlight off a reflective surface. The occurrence of a flash of radiation could result in the improper firing of the test weapon. On an open, outdoor test range which typically covers thousands of square meters, the probability of such an improper firing occurring is often too high to obtain the desired safety of operation.
Furthermore, the Griew system would require extensive modifications to transform a conventional weapon (either hand-held or vehicle-mounted) into one suitable for use on the test range. The Griew system also requires input from four detectors to the control circuit in order to determine whether the weapon should be enabled for firing. The required modifications shown for the Griew system are designed particularly for use with small firearms, and may not be suitable for the more complex firing mechanisms of larger weapons. It should be appreciated that the inclusion of the Griew control circuit into the firing mechanism of complex weaponry would require costly modifications. Also once a weapon is modified, it cannot be operated off the test range; custom built weapons for use only on the test range would be the net result. Further, the Griew system requires that the test weapon be connected through the control circuit to a guard ring of electromagnetic beams that inhibit the test weapon should an object interrupt any of the beams. It is impractical for a weapon to be physically or electromagnetically connected to a fixed position on an open range, which would be required if the guard ring of electromagnetic beams is used. Gun emplacement thus would be restricted to terrains suitable for maintaining contact with the guard ring.